Treatment of diseased tissues by various therapies is of vital importance in the medical community. Visualization of the treatment site is preferred; however, medical advances have provided improved methods, such as cardiac catheterization, which permits a physician to perform a medical procedure on the heart without ever directly observing the treatment site.
Cardiac catheterization includes the, use of a catheter, which delivers, for example, a fiber optic cable to the treatment site. Transmission of electromagnetic energy, such as laser light, through the fiber optic cable can then be used to coagulate blood vessels or cauterize tissue via photothermal treatment. It has been found desirable to utilize photothermal treatment for a variety of diseases, including heart disease and ischemic portions of the heart muscle. Photothermal treatment involves the delivery of optical energy to the desired site and the conversion of the optical energy into thermal energy.
Photothermal treatment of tissue has certain drawbacks associated with the positioning of the catheter and the fiber optic cable. For example, the heat that is generated can cause blood in the artery, vein, or atrium to coagulate and/or form a thrombosis. This misdirected energy may also prevent the treatment site from receiving what is believed to be the appropriate dose of therapeutic energy. These drawbacks are often associated with not being able to directly or indirectly visualize the treatment site.
Generally, the catheter is visualized by use of X-rays. The opacity of the catheter and its components, in comparison to the relative transparency of body tissues and fluids, permits the physician to determine the approximate location of the catheter. This method allows for some uncertainty in the exact placement of the fiber optic cable and catheter and does not inform the physician when the catheter is in contact with tissue. Alternatively, viewing the catheter endoscopically can monitor positioning of the fiber optic cable inside a patient. However, blood and other body fluids can obstruct the view of the physician, which can lead to imprecise positioning of the catheter. Either method does not allow the physician to always predict when the distal end of the catheter is in contact with the site that requires treatment.
A need therefor exists for a method and apparatus, which overcomes and circumvents the above-identified problems. In particular, there is a need for phototherapy systems that can optimize contact and/or control the delivery of phototherapy such that radiation is delivered only when a satisfactory degree of contact is achieved.
Methods and apparatus for phototherapy are disclosed in which laser light or other radiation is projected from within a catheter, through a balloon member, and toward the surface of tissue. In one embodiment, the light is projected in an annular pattern without requiring direct contact of the energy source, e.g. a laser (via fiber), with the targeted tissue. The light reflected from body fluids or the tissue surface is captured by a collecting device located within the catheter, e.g., within the balloon member, and the intensity of the reflected light (or a ratio of reflected light at certain wavelengths) is ascertained. Quantification of the reflected light provides the operator with information to determine when the catheter if positioned at the treatment site.
The balloon member of the catheter serves to force any remaining body fluids, such as blood, away from the treatment site. The absence of body fluids, such as blood, causes an increase in the amount of reflected light from the tissue surface, thereby indicating to the operator when the instrument is advantageously positioned against the treatment site. The invention is particularly useful in cardiac therapy in creating annular conduction blocks in atrial chamber tissue, e.g. centered about but at a defined distance from a pulmonary vein orifice or coronary sinus orifice, to eliminate aberrant wave conduction.
The invention is particularly useful for inducing phototherapeutic processes in tissue, including ablation and/or coagulation of the tissue. Typically the optical apparatus is contained within a catheter including a flexible elongate member having a proximal end, a distal end and at least one longitudinal lumen extending therebetween. The distal end of the flexible elongate member can be open or includes a transparent cap, a centering balloon, or a centering coil. The optical apparatus of the invention can be fixed at a distal location or preferably disposed within the first lumen in a manner that permits axial motion within the lumen. The optical apparatus serves to project light through, or from, the distal end of the flexible member of the catheter. The optical apparatus can include an optical fiber and other light projecting elements.
In certain embodiments, the optical apparatus of the invention is slidably positioned within the lumen of a catheter proximate to a tissue site. Positioning the optical apparatus at the particular location within the;balloon and/or by adjusting the size or shape of the balloon permits control over the size and distance of the forwardly projected light. In a preferred embodiment, the light is projected in an annular fashion as is described in pending U.S. patent application Ser. No. 09/602,420, filed Jun. 23, 2000, entitled xe2x80x9cPhototherapeutic Waveguide Apparatusxe2x80x9d, attorney docket number 101327-147, now allowed, which claims priority to U.S. patent application Ser. No. 09/357,355 filed on Jul. 14, 1999, now U.S. Pat. No. 6,423,055 the contents of which are incorporated herein by reference. This control permits the annular beam of projected light to be dynamically changed to specifically target the atrial tissue surrounding the pulmonary veins or coronary sinus.
In certain embodiments, the tissue forms a lumen, e.g., vascular, atrial, ventricular, arterial, venous, brachial, or urethral lumen. Preferably the methods include projecting an annular light pattern via an optical apparatus that is located at a defined distance from the target tissue.
In one embodiment of the present invention, the photoablation instrument includes an expandable balloon member adapted to surround the optical assembly upon inflation.
Injection of a solution or gas expands the balloon, thereby forcing blood and/or other body fluids from the tissue site. Preferably, the balloon member can be inflated with deuterium oxide or deuterated water, such that the inflated balloon provides a low loss transmission pathway for radiation between the optical assembly and the tissue surface. Deuterium oxide provides the advantage that it absorbs less energy from the transmitted energy, thereby preventing the balloon from becoming heated.
The optical apparatus, projects light through the catheter and balloon toward a tissue surface. Reflected light from the surrounding area is then captured by a collector. This xe2x80x9cfeedbackxe2x80x9d array is in communication with spectrophotometers and a computer, which can be used to determine when the instrument is positioned correctly at the treatment site. A region of tissue can then be exposed to radiation from the optical assembly both for determining whether the instrument is positioned properly as well as therapeutic treatment. The methods of the invention can be performed therapeutically or prophylactically.